Contact bodies of tungsten.



A. I. LIEBIVIANN @L w. A. MEGRATH.

CONTACT BODIES 0F TUNGSTEN.

APPLICATION FILED IIIAYzz. 1915.

1,155,421, Paten/Igea Im. 5,1915.

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ALFRED J'. LIEBMANN AND WILLIAM A. MEGRATH,

OF NEW YORK, N. Y., ASSIGNORS T0 INDEPENDENT LAMP AND WIRE COMPANY, INC., OF NEW YORK, `N. Y., A COR- PORATION OF NEW JERSEY.

CONTACT BODIES OF TUNGSTEN.

TAM-5,42*?.

Patented Oct. 5, 1915.

Original application led November 20, 1914, Serial No. 873,087. Divided and this application led May 22, 1915. Serial No. 29,777.

To all whom 'it may concern.'

Be it known that we, ALFRED J. LIEBMAN and lVILLIAM A. MEGRATH, respectively of the borough of Manhattan, city, county, and State of New York, and of the borough of Brooklyn, county of Kings', city and State of New York, have jointly invented certain new and useful Improvements in Contact Bodies of Tungsten, of which the following is a specification.

This application is a division of our application Serial No. 873,087 filed November 20th, i914.

This invention relates to improved electrical contacts for the use as contacts for gas engines, for circuit controllers and other like purposes.

As set forth in the Patent No. 1,111,698 granted September 22nd, 1914, to Alfred J. Liebmann, the met-al obtained by the invention covered thereby is suitable to be used for contacts for magnetos and similar devices where there is a frequent making and breaking of an electric current. In order to make the tungsten contact plate or disk suitable for such purposes, it is desirable and in some cases even necessary to fasten or secure it to another metal, which other metal is so shaped that it can be easily attached tothe apparatus in which the contact element is to be used. The tungsten plate or disk may be formed in any suitable way, for instance, it may be cut either from a plate of rolled tungsten or in cross sections from a rod or ingot of tungsten. The second metal as a rule is in the form and shape of a tack and suitablyy shaped to fit into some part which can be designed as the receptacle for the actual tungsten contact element.

Tt has been the practice to jointhe ltungsten contact plate or disk to the tack by means of an auxiliary third metal differentfrom the metals of the contact and support. We have invented a process whereby we can join the tungsten plate or disk to the tack without the aid of such an auxiliary third metal. That is, we weld the tungsten contact plate or disk directly to the holder or carrier or backing material, which is to be set into the apparatus and which as a whole can be described as ,a contact breaker. By means of our invention, an article is produced which is commercially superior to the tungsten contacts which have, as a rule, been used and which consist of a tungsten face plate and steel supporting tack soldered together by copper. Our new product consists only of a face plate of tungsten and a supporting metal back directly welded together by electric resistance welding without the aid of the copper or any third material of lower fusing point which might, during the operation of the circuit breaker, become hot, get soft and thereby make the tungsten contact lose connection from the metal backing and fall off. This danger is avoided by means of our invention in which the tungsten contact disk or plate is directly joined to the carrier metal which may be for instance iron or steel. The resulting element is, therefore, homogenous, and can almost be said to consist of one solid piece, the two pleces of metal being joined directly together and forming one undivided unit. Furthermore our device is easier and less expensive to manufacture.

Tn the practice of our invention we place between the two metals a point or a multitude of points of the same material either steel or tungsten which will oppose when a current of electricity is passed through the two metals, a higher resistance to the passing electric current, and therefore reach a very high temperature locally. This temperature will be highest where the surfaces of the two metals to be joined contact with the points or projections between them and thus cause the two metals to soften and weld together when the proper pressure is applied. We have also found that we can still heighten this effect by placing between the two metals, a chemical, which when the current is being passed and a high temperature is being reached, by its own chemical action, will intensify the heat, and at the same time polish and clean the surfaces of the two metals in such a way that they stick to each other much better or much more intimately and form a composite body much easier than when simply joined without this auxiliary chemical, which cleans the surfaces of any film of oXid or other foreign material which might be present. This chemical is so selected that it at the same time has a de-oxidizing action for both metals and We have found as most suitable for this purpose alkali or alkaline compounds, especially potassium nitrite. The reaction between potassium nitrite and tungsten, which is the sample given, is very highly exothermic, once started. This can easily be shown by a very simple experiment. If a cold piece of tungsten is dipped into a fusion of potassium nitrite, the reaction begins slowly, but after a very short time the piece of tungsten becomes red hot, even if no outside heat is applied. The fusion does not freeze, which it would do if the action were sudothermic: on the contrary, it becomes even hotter by the reaction.

Referring to the drawings; Figure 1 is an elevation showing a single point or projection for welding the tungsten contact to the iron or steel base. Fig. 2. is a plan view of the supporting tack shown in Fig. 1. Fig. 3. is a side elevation similar to Fig. 1 with a pluralityl of welding points or projections as shown. Fig. 4. is a plan of the supporting tack shown in Fig. 3. Fig. 5. is a side elevation of the supporting tack and tungsten plate having a multitude of welding projections on the head of the tack. Fig. 6. is a plan view of the supporting tack shown in Fig. 5. Fig. 7 is a side elevation of the supporting tack and tungsten contact plate with powdered tungsten metal therebetween. Fig. 8. is a plan view of the supporting tack shown in Fig. 7. having thereupon powdered tungsten metal. Fig. 9. is a side elevation of the supporting tack and contact plate showing both the welding points and the powdered tungsten metal therebetween. Fig. 10. is a plan Viewr` of the supporting tack with both the welding points or projections and the powdered metal tungsten thereupon shown in Fig. 9. Fig. 11. is a sectional view through the center of the supporting tack and Contact plate showing a recess in the center of the contact plate and a projection in the upper surface of the tack. Fig. 12. is a plan of the upper surface of the supporting tack shown in Fig. 11. Fig. 13. is a section of a supporting tack and contact plate in a position inverted from that shown in Fig. 1l, with powdered tungsten metal shown inthe recess. Fig. 14. is a plan of the under surface of the tungsten plate or disk shown in Fig. 13. Fig. l5 is an enlarged perspective View of our complete product. Fig. 16 is a conventional apparatus used in the carrying out of our process.

In the drawings, similar reference characters indicate like parts. i

10 represents the tungsten contact plate or disk, 11 an iron or steel supporting tack or base having a head 12 and a shank 13 depending therefrom. The line 1-1 (Fig. 15) represents the integral weld between the two metals. 14 represents the Welding points and 15 powdered tungsten metal and 1G is a cavity or recess in the tungsten contact plates or disks.

Referring to Fig. 16. 20 represents the upper electrode consisting of a rod of conducting material which is bent in a half circle and positioned in such a way as to come in contact with the center of the lower electrode 22, the two being pressed together by a suitable spring 24 or other suitable means. The upper electrode has a slight recess 21 in its center to hold the tungsten plate or disk 1() and thereby prevent it from sliding sdewise, and the lower electrode also has a slight recess 24: in its center to hold the iron or'steel supporting tack in place. Both electrodes are connected in circuit through the terminals 30 which also connect in circuit with a source of power 31 a rheostat 32, a measuring instrument 33 and a switehsl. The lower electrode is slidably mounted upon a fixed rod 40 and is supported in its upper position by a spring 24 situated between the electrode and a collar 41 mounted upon the rod 40 and held in place by a set screw 42 to adjust its position upon the rod.

A represents the main support, B the base, C an adjustable supporting arm, l) the bell, and E a tube through which hydrogen is passed into the bell.

Ve find that while we can carry out our process in the open air, that it is of advantage to carry it out either in a neutral atmosphere or vacuum, or even better, in an atmosphere which has a de-oxidizing action. "We find hydrogen of special advantage, which is almost obvious because it helps toV keep the two surfaces of the metal plates, which are to be joined together, clean, and prevents them from oxidizing. We have found, however, that we can carry out our process not only in vacuum or neutral atmosphere, but when using a cle-oxidizing chemical, as described. above, we have succeeded in making a perfect weld in the open air, an operation which heretofore has never been performed and has been considered impossible. It is of advantage from several points of view to do this. First the operation can be carried out much easier than under the bells or other vessels, as it is necessary when the work is carried out in a neutral atmosphere or vacuum, and second the electric current used can be moderated quite considerably as compared for instance with an atmosphere of hydrogen, which gas has a Very high thermal conductivity and carries away a good deal of the heat which is produced by the passage of the current.

To make our invention more clearly understood and adaptable to persons skilled in the art, we will hereafter describe several ways how it can be performed. For eX- ample we shall speak of tungsten as the one metal which will serve as the actual contact making substance, while the tack or carrier in this example will be assumed to be of iron or steel. IVe wish "it clearly understood. however, that instead of steel, another metal of comjmratively high melting point and of suitable physical properties can be used such as nickel, nickel alloys or others. In

'our example, we take for instance. a contact plate or disk of tungsten of a. diameter of approximately .13 and the height of which is .05. i

IVe have found several different ways to carry out the invention and according to these different ways. the tack to which the tungsten plate or disk will be attached, has to be shaped differently. In the first case, this tack has a small protruding point or projection preferably in the center of the disk. This point is preferably of conical shape and its point is naturallv directly over the center of the tack. While welding the point the tungsten plate is brought down on to this point in such a wav that its center is touched by the point of the projection. The tack and the tungsten plate in this position are brought between two electrodes which are suitably shaped as herein described. VVe now pass an electric current through the tack and the projection and the tungsten plate which brings the projection and that portion of the metal ofthe tack and tungsten plate adjacent thereto to a fusing or welding temperature, and the welding is completed upon compressing the two metals together. The iron or steel projection must be made of sufficient size to furnish enough fused material to fasten the tungsten plate to the tack. (lare should be eXercised not to make the projection too high. because in that case complete fusion would not take place and the two surfaces could not be pressed tightly together. In the proportionate junction. that is when use ing a tungsten plate of about 0.139 diameter and .05 in height. and a tack,I the supporting head of which is of the same height, the height of the iron or steel projection on the tack should be about .1 and its diameter about .08. Instead of using one point in the center of the tack, two or more of these points may be used. The projections should be smaller the larger their number. and it is an advantage to use very many of these points so that the surface of the tack has the appearance of a very rough tile orrasp. y In the two cases mentioned, the medium which furnishes the high resistance for the current and by its fusing joins and welds the two materials together, is iron or steel. In the third case we use tungsten or other similar material to that of the contact plate or disk. We could produce tungsten plates with a point the same as in the first case or a multitude of points the same as in the second case, but we have found that in some cases instead of fusing these points to the tungsten plate it is practical to use a. comparatively smooth tungsten plate, a coinparatively smooth steel tack and place between the two some powdered tungsten which provides a multitude of points or projections which create a very high resistance. For such purpose We have selected a coarse grain tungsten powder. When the current is passed through the tungsten plate powder and tack in arrangement of this kind, the tungsten powder between the two is fused and unites the two plates into a uniform piece. j

It is of great advantage to combine the second and third cases in such a way as to use the steel plate with a multitude of projecting points as described, and place on this plate the tungsten powder as mentioned. IVe then get a combined action and a uniform combined piece results. We have also found that in some instances it is of advantage to make a recess for the projections to set in. This recess if shaped at a. less angle than that of the point has the further advantage to provide two points of contact where the projection is placed. An additional high resistance therefore will eXist and consequently a high temperature will result when the current passes which causes the metal to fuse and flow into therecess filling it and causing the best binding in the center of the tack, or at the point where it is most desirable. In the case of a multitude of projections, a multitude of recesses is desirable, and while one of the plates, preferably the iron, has the projections, the other plate, that is the tungsten, should have the recesses. It can, however, be arranged the opposite way, but because of the different physical properties of the metals the softer metal is used, which requires the more working. That is to say, the recess is preferably made in the tungsten, because it is easier to form a recessthan to form a point of suitable lengtlr/ We have found it of advantage to use a chemical of the properties described heretofore, for instance powdered potassium nitrite, which we find to be most suitable for this purpose. The powdered material, in the case of the fixed point or fixed points, is simply strewn on the flat plate, upon which the other plate, which is provided with the projection, is lowered. rIhe moment the current is passed, the projection begins to glow, the chemical around it starts its action, and while developing local heat through this chemical action, it is cleaning and softening the surfaces, thereby preparing it for the intimate junction which results the moment the metal, which is of high resistance, fuses.

When using tungsten metal powder, We mix the tungsten powder with the potassium nitrite powder and place this mixture {between the tungsten plate and iron or steel tack. In the last case. that is when the welding is carried out in the air, we find the use of our chemical very useful. If it isnot used, the two plates have a tendency to break apart, although we have succeeded in a good many instances to join them without the use ot' the chemical.

lV hen working in hydrogen a current of about 1400 amperes is needed to thoroughly weld the two pieces together, in the first case, that is when a single projectionis used. W hen tungsten powder is only used, a current of about 1200 amperes is needed. vVhen in addition to the tungsten powder the chemical is used, it is sullcient to use a current of about 1000 amperes and in the case when the process was carried out in the open air, a current of about 700 amperes is sufficient to cause an ultimate junction of the two metallic plates.

What We claim as new and desire to obtain by Letters Patent, is:

rectly to each other by an eleqtrical resistance weld.

2. An electric mal e-and-b\1\aak contact 30 consisting only of a face plate of tungsten and a support of iron or steel Welded thereto.

In witness whereof we have hereunto set our hands at the borough of ,Manhattam city and State of New York, this tenth day 35 0f'Ma1-Ch, 1915.

ALFRED J. LIEBMANN. WM. A, MEGRATH.

In presence of- ETHEL D. BARON, JOHN J. RANAGAN. 

